Disc cartridge including an inner shell formed by severing a molded portion and a flanged thin-walled section

ABSTRACT

The present invention is related to a disc cartridge in which an optical disc, an inner shell and shutter members are housed in a main cartridge body unit, formed by abutting and combining upper and lower shells and in which the inner shell is run in rotation to cause the shutter members to open or close an aperture provided in the main cartridge body unit. The inner shell is formed by a resin molding portion comprised of a first molded portion for forming the inner shell and a second molded portion connected to the first molded portion. The second molded portion is provided at a position forming the aperture in the inner shell and is connected to the first molded portion through a flanged thin-walled section. The inner shell is formed by severing the second molded portion and the flanged thin-walled section.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 10/363,056, filed Feb. 27, 2003 now U.S. Pat. No. 7,017,170.

TECHNICAL FIELD

This invention relates to a disc cartridge, including a disc-shapedrecording medium, such as an optical disc, a magneto-optical disc or amagnetic disc, housed for rotation within a main cartridge member, amolding member for molding a member which is to form this disccartridge, and a method for producing an inner shell.

BACKGROUND ART

Up to now, a disc cartridge comprised of a disc-shaped recording medium,such as an optical disc, a magneto-optical disc or a magnetic disc,arranged for rotation within a main cartridge member, has beenextensively used. This sort of the disc cartridge accommodates adisc-shaped recording medium, on which information signals, such asaudio or video signal or program data have been already recorded or areto be recorded. The disc-shaped recording medium, on which theinformation signals can be recorded, may be enumerated by a write-oncedisc, which allows to record the information signals only once, and arewritable optical disc, such as a magneto-optical disc, which allowsfor re-recording information signals.

As a disc cartridge, accommodating therein a disc-shaped recordingmedium on which information signals have been already recorded or are tobe recorded, such a one shown in FIG. 1 is in use. A disc cartridge 500,shown in FIG. 1, accommodates an optical disc 502, which enablesinformation signals to be recorded, and includes a main cartridge bodyunit 501, made up by an upper shell 501 a and a lower shell 501 b, andan optical disc 502 rotatably housed therein. The upper shell 501 a andthe lower shell 501 b, making up the main cartridge body unit 501, areeach formed with a recording and/or reproducing aperture 503 forexposing a portion of the optical disc 502 to outside. On the maincartridge body unit 501, there is movably mounted a shutter member 504for opening/closing the aperture 503. Centrally of the optical disc 502is mounted a chuck plate 505 for chucking on a turntable of a discdriving device, which is adapted for rotationally driving the opticaldisc 502.

When the disc cartridge 500 is mounted in a cartridge mounting positionin the disc driving device, the shutter member 504 is slid to open therecording and/or reproducing aperture 503, while the optical disc 502 isloaded on the turntable. At this time, the chuck plate is sucked by amagnet provided on the turntable, so that the optical disc is now ableto be rotated in unison with the turntable. If then a spindle motor isrun in rotation, the optical disc 502 is rotated at a constant linearvelocity. At this time, the shutter member 504 is moved, so that theoptical head faces the optical disc 502 via the opened recording and/orreproducing aperture 503. As the optical head is moved radially of theoptical disc 502, and a signal recording area of the optical disc 502 isscanned by a light beam radiated from the optical head, the informationsignals recorded on the optical disc 502 are read out by the light beamradiated from the optical head, or the information signals are recordedon the optical disc 502.

Meanwhile, in an optical disc, accommodated in a disc cartridge, therecording density tends to be increased, in keeping pace with theincreasing recording capacity, such that the recording pattern tends tobe narrowed in pitch, while tending to be higher in line density. If,with the optical disc in which the recording density is increased inkeeping pace with the increasing recording capacity, dust and dirt ofminute size become affixed to the signal recording surface, the lightbeam from the optical head is thereby interrupted to disable correctrecording and/or reproduction of information signals.

With the above-described conventional disc cartridge 500, since theshutter member 504 of a substantially U-shaped cross-section is fittedon the outer side of the main cartridge body unit 501 so as to bemovable relative to the main cartridge body unit 501, there is likely tobe produced a gap intermediate the main cartridge body unit 501 and theshutter member 504, such that intrusion of dust and dirt cannot beprohibited satisfactorily. As a consequence, dust and dirt are intrudedinto the inside of the main cartridge body unit 501 so as to bedeposited on the optical disc accommodated therein.

With this disc cartridge 500, in which the shutter member 504 is mountedoutside the main cartridge body unit 501, there is a fear that the userinadvertently moves the shutter member 504 to open the recording and/orreproducing aperture 503. Since the shutter member 504 is linearly movedalong a lateral side of the main cartridge body unit 501, the size ratioof the shutter member 504 relative to the main cartridge body unit 501is increased, so that it is difficult to reduce the size of the shuttermember 504 and of the main cartridge body unit 501.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a noveldisc cartridge not suffering from the above-described deficiencyinherent in the conventional disc cartridge.

It is another object of the present invention to provide a disccartridge having a superior effect in dust or dirt proofing effect whichdoes not allow for intrusion of the dust or dirt of the minute size intothe inside of the main cartridge body unit accommodating a disc-shapedrecording medium.

It is a further object of the present invention to provide a disccartridge in which reduction in size and thickness may be achieveddespite the fact that an aperture having a large aperture ratio isprovided in the main cartridge body unit and that a large sized shuttermember is used for opening/closing the aperture.

It is a further object of the present invention to provide a disccartridge in which, in recording and/or reproducing information signalson or from a disc-shaped recording medium, the recording and/orreproducing head may be approached to the disc-shaped recording mediumaccommodated within the main cartridge body unit, and in which, evenwhen the recording and/or reproducing head is approached to thedisc-shaped recording medium, the recording and/or reproducing head maybe prohibited from interfering with the disc-shaped recording medium.

It is yet another object of the present invention to provide a moldingmember for a synthetic resin which allows for casting a disc cartridge,superior in the effect of preventing intrusion of dust and dirteliminating into he main cartridge body unit, to high accuracy withoutmolding distortion or warping.

The present invention provides a disc cartridge in which a disc-shapedrecording medium, an inner shell, and a shutter member are mountedwithin a main cartridge body unit, obtained on combining an upper shelland a lower shell by having respective peripheral wall sections of theupper and lower shells abutted and combined to each other, and in which,by rotating the inner shell, the shutter member is movable between afirst position and a second position, the first position being such aone that the shutter member closes an aperture provided in the maincartridge body unit for exposing at least a portion of the disc-shapedrecording medium to outside along the radial direction of thedisc-shaped recording medium, the second position being such a one thatthe aperture is opened. A crank-shaped dust intrusion prohibiting unitis provided inwardly of the peripheral wall sections of the upper andlower shells abutted to each other for preventing intrusion of dust fromthe abutting surfaces of the peripheral wall sections of the upper andlower shells towards the disc-shaped recording medium housed within themain cartridge body unit.

With the disc cartridge of the present invention, a disc-shapedrecording medium, an inner shell, and a shutter member are mountedwithin a main cartridge body unit, obtained on combining an upper shelland a lower shell by having respective peripheral wall sections thereofabutted to each other, and in which, by rotating the inner shell, theshutter member is movable between a first position and a secondposition, with the first position being such a one that the shuttermember closes an aperture provided in the main cartridge body unit forexposing at least a portion of the disc-shaped recording medium tooutside along the radial direction of the disc-shaped recording medium,and with the second position being such a one that the aperture isopened. A crank-shaped dust intrusion prohibiting unit for prohibitingintrusion towards the disc-shaped recording medium housed in the maincartridge body unit from the aperture is provided on a slide contactsurface between at least one of the upper and lower shells and theshutter member.

With the disc cartridge of the present invention, since the shuttermember is provided in the main cartridge body unit, the user may beprohibited from inadvertently sliding the shutter member. With the disccartridge of the present invention, the crank-shaped dust intrusionprohibiting unit is provided for inhibiting intrusion of dust and dirtfrom the abutment surfaces of the peripheral wall sections of the upperand lower shells towards the disc-shaped recording medium, thecrank-shaped dust intrusion prohibiting unit is provided on the slidecontact surfaces of the shell and the shutter for prohibiting intrusionof dust and dirt from the aperture towards the disc-shaped recordingmedium, and further the indented dust intrusion prohibiting unit isprovided for reliably prohibiting intrusion of dust and dirt into themain cartridge body unit to prevent micro-sized dust and dirt from beingaffixed to the disc-shaped recording medium accommodated in the maincartridge body unit to deteriorate recording and/or reproducingcharacteristics.

The present invention also provides a disc cartridge including adisc-shaped recording medium, a main cartridge body unit including anupper shell and a lower shell, the peripheral wall sections of whichabut against each other, the main cartridge body unit accommodating thedisc-shaped recording medium for rotation therein, at least a portion ofthe peripheral wall section of the lower shell being opened to form anopen end, with an aperture being formed in the main cartridge body unitbeginning from the open end for exposing a portion of the disc-shapedrecording medium to outside across the inner and outer rims of thedisc-shaped recording medium, an inner shell engaged in a guide grooveformed between an outer peripheral wall section and an inner peripheralwall section of the upper shell so as to be supported for rotationtherein, the inner shell including a connecting portion engaged in theguide groove, the inner shell also including an aperture in registerwith the aperture in the main cartridge body unit, and a shutter membermovable by rotation of the inner shell between a position closing theaperture in the main cartridge body unit and a position opening theaperture in the main cartridge body unit. The connecting portion of theinner shell is set to a height such that the connecting portion is notprotruded towards the lower shell relative to the lower surface of thedisc-shaped recording medium.

With the present disc cartridge, the connecting portion of the innershell is set to a height such that the connecting portion is notprojected towards the lower shell relative to the lower surface of thedisc-shaped recording medium, so that, as the head for recording and/orreproducing information signals for a disc-shaped recording medium isapproached towards the disc-shaped recording medium, it may besatisfactorily introduced into the inside of the main cartridge bodyunit, through the aperture in the main cartridge body unit and theaperture in the inner shell, from outside the outer rim of the maincartridge body unit, thus enabling the disc cartridge to be reduced inthickness.

The present invention also provides a disc cartridge including adisc-shaped recording medium, a main cartridge body unit including anupper shell and a lower shell, the peripheral wall sections of whichabut against each other, the main cartridge body unit accommodating thedisc-shaped recording medium for rotation therein, at least a portion ofthe peripheral wall section of the lower shell being opened to form anopen end, with an aperture being formed in the main cartridge body unitbeginning from the open end for exposing a portion of the disc-shapedrecording medium to outside across the inner and outer rims of thedisc-shaped recording medium, an inner shell engaged in a guide grooveformed between an outer peripheral wall section and an inner peripheralwall section of the upper shell so as to be supported for rotationtherein, the inner shell including a connecting portion engaged in theguide groove, the inner shell also including an aperture in registerwith the aperture in the main cartridge body unit, and a shutter membermovable by rotation of the inner shell between a position closing theaperture in the main cartridge body unit and a position opening theaperture in the main cartridge body unit. The inner shell is formed by aresin molding portion comprised of a first molded portion for formingthe inner shell and a second molded portion formed as one with the firstmolded portion. The second molded portion is provided at a positionforming the aperture in the inner shell, and is connected to the firstmolded portion through a flanged thin-walled section. The inner shell isformed on severing the second molded portion and the flanged thin-walledsection.

The present invention also provides a molded member for a disc cartridgeincluding a first molded portion, provided with a recording and/orreproducing aperture, and a second molded portion having a resininjection port and molded at a position where the aperture is formed.The first and second molded portions are formed as one with each otherthrough a flanged thin-walled section. The first molded portion is aninner shell formed to approximately a disc shape and rotatablyaccommodated in a disc cartridge accommodating a disc-shaped recordingmedium therein. The inner shell is adapted for opening/closing aplate-shaped shutter member provided in the disc cartridge.

The present invention also provides a method for producing an innershell used for a disc cartridge, the disc cartridge including adisc-shaped recording medium, a main cartridge body unit including anupper shell and a lower shell the peripheral wall sections of which abutagainst each other, the main cartridge body unit accommodating thedisc-shaped recording medium for rotation therein, at least a portion ofthe peripheral wall section of the lower shell being opened to form anopen end, with an aperture being formed in the main cartridge body unitbeginning from the open end for exposing a portion of the disc-shapedrecording medium to outside across the inner and outer rims of thedisc-shaped recording medium, an inner shell engaged in a guide grooveformed between an outer peripheral wall section and an inner peripheralwall section of the upper shell so as to be supported for rotationtherein, the inner shell including a connecting portion engaged in theguide groove, the inner shell also including an aperture in registerwith the aperture in the main cartridge body unit, and a shutter membermovable by rotation of the inner shell between a position closing theaperture in the main cartridge body unit and a position opening theaperture in the main cartridge body unit. The inner shell includes afirst molded portion, provided with a recording and/or reproducingaperture, and a second molded portion having a resin injection port andmolded at a position where the aperture is formed, and a flangedthin-walled section connecting the first and second molded portions asone to each other. The method includes the steps of injecting moltenresin into a cavity defined by a fixed metal die and a movable metal diefor molding the first molded portion, second molded portion and theflanged thin-walled section and severing the flanged thin-walled sectionby a punch provided to the movable metal die before the molten resininjected into the cavity is cooled and solidified.

Other objects, features and advantages of the present invention willbecome more apparent from reading the embodiments of the presentinvention as shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an example of a conventional disccartridge.

FIG. 2 is a perspective view showing a disc cartridge according to thepresent invention, looking from a side upper shell.

FIG. 3 is an exploded perspective view of the disc cartridge accordingto the present invention, looking from the side upper shell.

FIG. 4 is a perspective view showing a disc cartridge according to thepresent invention, looking from the side lower shell.

FIG. 5 is an exploded perspective view showing a disc cartridgeaccording to the present invention, looking from the side lower shell.

FIG. 6 is a plan view showing the side inner surface of an upper shellforming the disc cartridge according to the present invention and

FIG. 7 is a plan view showing the side inner surface of a lower shell.

FIG. 8 is an enlarged cross-sectional view showing junction portions ofthe upper and lower shells making up the disc cartridge according to thepresent invention.

FIG. 9 is a cross-sectional view taken along line A–A′ in FIG. 2.

FIG. 10 is a see-through plan view showing an open position of an innershell relative to the main cartridge body unit in the disc cartridge ofthe present invention.

FIG. 11 is a see-through plan view showing a closure position of aninner shell relative to the main cartridge body unit in the disccartridge of the present invention.

FIG. 12 is a perspective view showing the shutter member forming thedisc cartridge according to the present invention for the side uppershell and

FIG. 13 is a perspective view showing the shutter member forming thedisc cartridge according to the present invention.

FIG. 14 is a perspective view showing the open position of the shuttermember relative to the inner shell and

FIG. 15 is a perspective view showing the open position of the shuttermember relative to the inner shell, in the disc cartridge according tothe present invention.

FIG. 16 is an enlarged cross-sectional view showing engaged portions ofthe inner shell and the shutter member.

FIG. 17 is a perspective view showing a disc driving device used in adisc cartridge according to the present invention.

FIG. 18 is a see-through plan view for illustrating the opening/closurestates of the aperture provided in the main cartridge body unit, andparticularly showing the completely closed state of the aperture.

FIG. 19 is a schematic cross-sectional view for illustrating theopening/closure states of the aperture provided in the main cartridgebody unit, and particularly showing the state in which a lift-up lug onthe side inner shell rides over a lift-up lug on the side upper shell.

FIG. 20 is a schematic cross-sectional view for illustrating theopening/closure states of the aperture provided in the main cartridgebody unit, and particularly showing the state in which the lift-up lugon the side inner shell and the lift-up lug on the side upper shell havebecome disengaged from each other.

FIG. 21 is a see-through plan view for illustrating the opening/closurestates of the aperture provided in the main cartridge body unit, andparticularly showing the state in which the aperture has slightly beenopened,

FIG. 22 is a see-through plan view for illustrating state in which theaperture has further slightly been opened,

FIG. 23 is a see-through plan view for illustrating the state in whichthe aperture has additionally slightly been opened, and

FIG. 24 is a see-through plan view for illustrating state in which theaperture has furthermore additionally slightly been opened.

FIG. 25 is a see-through plan view for illustrating state in which theaperture provided in the main cartridge body unit has completely beenopened.

FIG. 26 is a schematic perspective view showing the opened position ofthe inner shell relative to the upper shell in a disc cartridgeaccording to the present invention.

FIG. 27 is a cross-sectional view taken along line B–B′ in FIG. 26.

FIG. 28 is a perspective view showing a cast resin component, formingthe inner shell, looking from the side upper surface, and

FIG. 29 is a perspective view similar to FIG. 28 but looking from thelower surface side.

FIG. 30 is a perspective view showing the state in which a first castcomponent has been separated from the resin casting mass, looking fromthe side upper surface, and

FIG. 31 is a perspective view similar to FIG. 29 but looking from theside lower surface.

FIG. 32 is a cross-sectional view showing a resin casting device forcasting the resin cast mass.

FIG. 33 is a perspective view showing the resin cast mass forillustrating the flow of molten resin.

FIG. 34 is a perspective view showing a gate cut punch device forseparating the first cast product from the resin cast mass.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings, a disc cartridge embodying the presentinvention will be explained in detail.

Referring to FIGS. 2 to 5, a disc cartridge 1 embodying the presentinvention includes an optical disc 3, as a disc-shaped recording medium,an inner shell 4, and a pair of shutter members 5 a and 5 b.

A main cartridge body unit 2 includes an upper shell 6 and a lower shell7 combined with each other.

Referring to FIGS. 2, 5 and 6, the upper shell 6 is formed by injectionmolding a thermoplastic resin material, such as acrylonitrile butadienestyrene (ABS). The upper shell 6 has a substantially rectangular majorsurface, with its front side edge, adapted for being introduced into adisc driving device 70, as later explained, being shaped arcuately. Theupper shell 6 includes an outer peripheral wall 8, as a sidewall of themain cartridge body unit 2, mounted upright along the outer periphery ofthe major surface. At a mid portion of the front surface of the outerperipheral wall 8 is formed a first pickup intrusion recess 9, intowhich an optical head 79 of the disc driving device 70 is to beintruded, as later explained. At a mid portion of the rear surface ofthe outer peripheral wall 8 is formed a positioning recess 10 forpositioning the upper shell 6 relative to the lower shell 7. Therecesses 9, 10 are each formed as a cut-out of a preset width. On theinner peripheral side of the outer peripheral wall 8 is set upright asubstantially toroidally-shaped inner peripheral wall 11 forming a discaccommodating section. At a mid portion of the front side of the innerperipheral wall 11 is formed a second pickup intrusion recess 12, inwhich an optical head 79 of the disc driving device 70 as laterexplained is to be intruded. The second pickup intrusion recess 12 issimilarly formed as a cut-out of a preset width.

On the outer peripheral side of the inner peripheral wall 11 is formed asubstantially toroidally-shaped guide groove 13 for encircling the innerperipheral wall 11. In this guide groove 13 is rotatably engaged theinner shell 4. On the bottom surface of the guide groove 13 areprotuberantly formed a pair of lift-up lugs 14 for moving the innershell 4 in a direction away from the upper shell 6.

An upper corner peripheral wall 15 for preventing intrusion of dust anddirt is formed upright at three 6 b, 6 c and 6 d of the four corners 6a, 6 b, 6 c and 6 d, with the exclusion of the corner 6 a on the frontsurface side forming a lock accommodating section. This upper cornerperipheral wall 15 is formed for defining the periphery of the uppershell intermediate the outer peripheral wall 8 and the guide groove 13.A first groove 16 is formed intermediate the upper corner peripheralwall 15 and the outer peripheral wall 8, while a second groove 17 isformed intermediate the upper corner peripheral wall 15 and the guidegroove 13.

An upper tab peripheral wall 18, forming a tab accommodating section, ismounted upright at the corner 6 c on the back side opposite to thecorner 6 a of the front side of the upper shell 6. This upper tabperipheral wall 18 is formed intermediate the outer peripheral wall 8and the upper corner peripheral wall 15 for surrounding the corner 6 con the back side together with the outer peripheral wall 8. A thirdgroove 19 is formed intermediate the upper tab peripheral wall 18 andthe upper corner peripheral wall 15.

In the vicinity of the corners 6 a to 6 d of the upper shell 6, there isprotuberantly formed a substantially columnar-shaped positioning pin 20,at a mid portion of which is formed a tapped hole.

Referring to FIGS. 3, 4 and 7, the lower shell 7 is formed by injectionmolding a thermoplastic resin, such as acrylonitrile butadiene styrene(ABS), as is the upper shell 6. The lower shell 7 has a substantiallyrectangular major surface, with its front side edge, adapted for beingintroduced into the disc driving device, as later explained, beingshaped arcuately. The lower shell 7 includes an outer peripheral wall21, mounted upright along the outer periphery of the major surface forserving as a sidewall of the main cartridge body unit.

To the distal end of the outer peripheral wall 21, there are mountedupright a positioning peripheral wall 22, engaged in the positioningrecess 10 formed in the upper shell 6 for positioning the upper shell 6and the lower shell 7, and a dust-proofing peripheral wall 23 engaged inthe first groove 16 in the upper shell 6 for preventing dust from beingintruded from the space between the upper and lower shells 6, 7. Thatis, the positioning peripheral wall 22 on the upper shell 6 and thedust-proofing peripheral wall 23 on the lower shell 7 are abutted to andcombined with each other to make up a cranked first dust intrusionprohibiting section 21A for preventing dust and dirt from being intrudedfrom the outside into the inside of the main cartridge body unit 2accommodating the optical disc 3.

The lower shell 7 includes a substantially rectangular-shaped apertureportion 24 a, formed by opening the front mid portion of the outerperipheral wall 21 to a predetermined width for exposing a portion ofthe optical disc 3 to outside across the inner and outer rims of thedisc, and a substantially circular aperture portion 24 b for exposing acenter opening 3 a of the optical disc 3 to outside. Specifically, thislower shell 7 includes the recording and/or reproducing aperture portion24 a dimensioned to be large enough to permit the optical head of thedisc driving device, as later explained, to be intruded into the insideof the main cartridge body unit 2, and the driving aperture portion 24 bdimensioned to be large enough to permit a turntable 78 of the discdriving device 70 as later explained to be intruded into the inside ofthe main cartridge body unit 2, with the aperture portions 24 a, 24 btogether defining a sole aperture 24 opened to a mid portion of thefront side of the outer peripheral wall 21. Meanwhile, the first andsecond pickup intrusion recesses 9, 12 of the upper shell 6 are of awidth substantially coincident with the width of the aperture 24.

At the corner 7 a, from among the corners 7 a to 7 d of the lower shell7, on the front side of the lower shell 7, forming a lock accommodatingsection, there is protuberantly formed a supporting shaft 25 forrotatably supporting a lock member 29, which will be explainedsubsequently. At the remaining three corners 7 b to 7 d, excluding thecorner 7 a, of the front side of the lower shell 7, there is formedupright a substantially arcuate lower corner peripheral wall 26 engagedin the second groove 17 of the upper shell 6 described above. On therear side corner 7 c, opposite to the front side corner 7 a, of thelower shell 7, there is formed upright a lower tab peripheral wall 27engaged in a third groove 19 of the upper shell 6 described above. Thelower shell 7 is formed with a substantially cylindrically-shapedpositioning cap 28 engaged with the positioning pin 20 of the uppershell 6. A through-hole, not shown, is bored through the bottom of thepositioning cap 28.

The main cartridge body unit 2 is formed by superposing the upper andlower shells 6, 7 as the respective peripheral wall sections 8, 21 areabutted against each other.

At this time, the positioning recess 10 of the upper shell 6 is engagedwith the positioning peripheral wall 22 of the lower shell 7. On theother hand, the positioning pin 20 of the upper shell 6 and thepositioning cap 28 of the lower shell 7 are engaged with each other. Aset screw, not shown, is threaded into the tapped hole in thepositioning pin 20 through the through-hole of the positioning cap 28.In the first groove 16, second groove 17 and the third groove 19 of theupper shell 6, the dust-proofing peripheral wall 23, lower cornerperipheral wall 26 and the lower tab peripheral wall 27 on the lowershell 7 are engaged, respectively.

If, as shown in FIG. 8, the height of the outer peripheral wall 8 of theupper shell 6 is H1, the height of the outer peripheral wall 21 of thelower shell 7 is H2 and the inner height of the main cartridge body unit2 is H3, with H3=H1+H2, the upper corner peripheral wall 15, lowercorner peripheral wall 26, upper tab peripheral wall 18 and the lowertab peripheral wall 27 are each of a height H3. The dust-proofingperipheral wall 23 is of a height H1, with an inner rim side clearance Cbetween the dust-proofing peripheral wall 23 and the first groove 16being not less than 0.1 mm and not larger than 0.5 mm. This enablesintrusion of dust and dirt to be prevented without detracting from theease with which the upper and lower shells 6, 7 are put together.

Thus, with the main cartridge body unit 2, since an abutment surface Sbetween the positioning peripheral wall 22 of the upper shell 6 and thedust-proofing peripheral wall 23 of the lower shell 7, abutted andcombined to each other to form the first dust intrusion prohibitingsection 21A, is crank-shaped, it is possible to prevent dust and dirtfrom being intruded into the inside of the main cartridge body unit 2from a space between the outer peripheral wall 8 of the upper shell 6and the outer peripheral wall 21 of the lower shell 7.

Referring to FIGS. 3 to 5, the upper and lower shells 6, 7 aresuperposed one on the other to form a disc housing section in a midportion of the main cartridge body unit 2 for rotatably accommodatingthe optical disc 3, while a lock housing section for rotatablyaccommodating the lock member 29 is formed at one front side corner anda tab housing section for slidably accommodating a tab member 30 isformed at one rear side corner.

The lock member 29 performs the role of restraining the rotation of theinner shell 4 when the inner shell 4 is at a position of closing theaperture 24 of the main cartridge body unit 2. This lock member 29includes an engagement opening 31, rotationally engaged with thesupporting shaft 25 of the lower shell 7, an operating piece 32 extendedfrom the engagement opening 31 towards one lateral side of the maincartridge body unit 2, a stopper piece 33 extending from the engagementopening 31 towards the disc housing section, and a spring piece 34extended from this engagement opening 31 towards the inner lateralsurface on the front side of the main cartridge body unit 2. The distalend of the operating piece 32 includes an operating lug 32 a exposed tooutside from a lock opening 35 a formed in a lateral surface of the maincartridge body unit 2. The distal end of the stopper piece 33 includes astopper boss 33 a which is in sliding contact with a ring 43 of theinner shell 4, as later explained. The spring piece 34 is abutted in anelastically deflected state against the front inner surface of the maincartridge body unit 2.

Consequently, the lock member 29 is biased, under the force of thespring piece 34, in a direction in which the operating lug 32 a of theoperating piece 32 is protruded via the lock opening 35 a, and in adirection in which the stopper boss 33 a of the stopper piece 33 isabutted against the ring 43 of the inner shell 4. This lock member 29 isswung, by the operating lug 32 a of the operating piece 32 being thrust,such that the stopper piece 33 is moved in a direction away from thering 43 provided on the outer periphery of the inner shell 4.

The tab member 30 performs the role of preventing inadvertent erasure ofinformation signals recorded on the optical disc 3. Specifically, thistab member 30 includes a an operating lug, exposed to outside via a tabopening formed in a lateral surface on the back side of the maincartridge body unit 2, and a switching lug engaged in a pair ofswitching recesses formed in an upper tab peripheral wall. The tabmember 30 is slid by the operating lug being acted on so that theswitching lug is engaged with one of the paired switching recesses toeffect switching as to whether or not the information signals can berecorded on the optical disc 3.

On a lateral surface of the main cartridge body unit 2 is formed a guidegroove 36 for extending in the fore-and-aft direction. The guide groove36 is aimed to prevent mistaken insertion of the disc cartridge 1 at thetime of loading thereof on the disc driving device 70 which will beexplained subsequently. On the bottom surface of the guide groove 36 aresequentially formed, looking from the side front surface, the lockopening 35 a, through which the operating lug 32 a of the lock member 29is exposed to outside, and an opening for a rotor 35 b, through whichthe outer periphery of the inner shell 4 is partially exposed tooutside.

In the upper surface of the main cartridge body unit 2 is formed asee-through window 37 through which the optical disc 3 housed thereinmay be viewed. In the lower surface of the main cartridge body unit 2are formed a plurality of positioning recesses 38 for effectingpositioning at the time of loading the main cartridge body unit 2 on thedisc driving device 70 which will be explained subsequently. In bothlateral sides of the main cartridge body unit 2 are formed pluralcut-outs 39 for positioning at the time of loading the disc cartridge 1on the disc driving device 70 and for discriminating the disc cartridgetype.

The optical disc 3 is substantially in the form of a disc having thecenter opening 3 a, and is housed for rotation in the inside of theabove-described main cartridge body unit 2, as shown in FIGS. 3 and 5.The center portion of the optical disc 3 is pressed by a chuck plate 40when the optical disc is chucked on the turntable 78 of the disc drivingdevice 70 as later explained. This chuck plate 40 is substantiallydisc-shaped and is formed of a metallic material attractable by amagnet. The chuck plate 40 has its mid portion swollen to form a discthrusting portion 40 a adapted for thrusting the center portion of theoptical disc 3.

A plate housing recess 41, adapted for rotatably holding the chuck plate40, is formed centrally of the upper shell 6. In the plate housingrecess 41 is fitted a plate retainer 42 for holding the chuck plate 40therein. The plate retainer 42 is provided with a fitting opening 42 a,in which is fitted a thrusting portion 40 a. The plate retainer is alsoprovided with an engagement recess 42 b, engaged by the outer peripheryof the chuck plate 40, such as to surround the fitting opening 42 a.

Thus, the chuck plate 40 is rotatably accommodated in the inner spacedefined by the plate housing recess 41 and the plate retainer 42, as thedisc thrusting portion 40 a is protruded via the fitting opening 42 a ofthe plate retainer 42, as shown in FIG. 9.

The optical disc 3, accommodated in the main cartridge body unit 2, maybe enumerated by a replay-only optical disc, having pre-recorded thereonaudio data corresponding to audio content data, or video datacorresponding to video content data, a write-once optical disc, capableof writing the information signals only once and a rewritable opticaldisc capable of repeatedly rewriting the information signals. Thedisc-shaped recording medium may be enumerated by a magneto-optical discor a magnetic disc, in addition to the aforementioned optical disc 3.

The inner shell 4, equivalent to an intermediate shell, arranged withinthe main cartridge body unit 2, is formed by injection molding athermoplastic resin material, such as polyoxymethylene (POM), as shownin FIGS. 3 and 5. The inner shell 4 is substantially disc-shaped andincludes a substantially toroidally-shaped ring 43 engaged in the guidegroove 13 of the upper shell 6. The inner shell 4 is rotatably supportedwith respect to the main cartridge body unit 2 by the ring 43 engagingin the guide groove 13 of the upper shell 6. The inner shell 4 alsoincludes an aperture 44 corresponding to the recording and/orreproducing aperture 24 formed in the lower shell 7. The portion of thering 43 on the outer periphery of the inner shell 4, lying at the openend of the aperture 44, operates as a connecting portion 43 for bridgingthe open end side of the aperture 44.

On the outer peripheral surface of the ring 43 is formed a gear 45 forrotating the inner shell 4. This gear 45 is formed between a positionopened to outside from the front surface side of the opening for therotor 35 b, with the inner shell 4 then being in the closed positionshown in FIG. 10, and a position opened to outside from the side backsurface of the opening for the rotor 35 b, with the inner shell 4 thenbeing in the open position shown in FIG. 11.

On the outer peripheral surface of the ring 43 are formed a pair ofstopper projections 46 a, 46 b, at a preset spacing from each other, forcontrolling the amount of rotation of the inner shell 4. The upper shell6 is provided with a pair of stopper receiving portions 47 a, 47 b,between the guide groove 13 and the upper corner peripheral wall 15, soas to be abutted by the stopper projections 46 a, 46 b, respectively.When the inner shell 4 is rotated clockwise in FIG. 11, the stopperprojection 46 a abuts on the stopper receiving portion 47 a to impedefurther rotation of the inner shell 4. At this time, the inner shell 4is in its opened position, with the aperture 44 of the inner shell 4being substantially coincident with the aperture 24 of the maincartridge body unit 2. On the other hand, when the inner shell 4 isrotated counterclockwise in FIG. 10, the stopper projection 46 b abutson the stopper receiving portion 47 b to impede further rotation of theinner shell 4. At this time, the inner shell 4 is in its closedposition, with the aperture 44 of the inner shell 4 being tilted to themaximum extent with respect to the aperture 24 of the main cartridgebody unit 2.

On the foremost end face of the ring 43 are protuberantly formed a pairof lift-up lugs 48 adapted for having sliding contact with a pair oflift-up lugs 14 of the guide groove 13, as shown in FIGS. 10 and 11.When the inner shell 4 is in proximity to the closure position, thelift-up lugs 48 ride on the lift-up lugs 14 of the guide groove 13, asthe lift-up lugs 48 are in sliding contact therewith, such that theinner shell 4 is lifted in a direction away from the upper shell 6.

On the major surface of the inner shell 4 opposite to its surface fromwhich projects the ring 43 are formed a pair of supporting shafts 49 a,49 b, adapted for rotationally supporting a pair of shutter members 5 a,5 b, respectively, as shown in FIG. 5. These supporting shafts areprovided at point-symmetrical positions with respect to the center ofthe inner shell 4, that is with a phase difference of 180° to eachother.

The paired shutter members 5 a, 5 b are shaped point-symmetricallyrelative to each other and are rotatably mounted with a phase differenceof 180° about the paired supporting shafts 49 a, 49 b of the inner shell4, as the center of rotation, as shown in FIGS. 12 and 13. Theequivalent parts or components of the paired shutter members 5 a, 5 bare denoted by the same reference numerals. Similarly to the inner shell4, the shutter members 5 a, 5 b are formed by injection molding athermoplastic resin material, such as polyoxymethylene (POM). Theshutter members 5 a, 5 b are each in the form of substantiallysemi-circular flat plate. The proximal ends of the shutter members 5 a,5 b are formed with engagement openings 50 a, 50 b engaged by therotatable supporting shafts 49 a, 49 b of the inner shell 4.

On chord portions of the paired shutter members 5 a, 5 b, acting as theabutment surfaces thereof, there are formed a first abutment surfacesection 51, extending from the center portion towards the proximal end,and a second abutment surface section 52, extending from the centerportion towards the distal end. Of these abutment surface sections, thefirst abutment surface section 51 has its side towards the lower shell 7formed as an inclined surface, while the second abutment surface section52 has its side towards the upper shell 6 formed as an inclined surface.The shutter members 5 a, 5 b are rotated in a direction towards and awayfrom each other, about the supporting shafts 49 a, 49 b of the innershell 4 as the center of rotation, such that the first abutment surfacesection 51 of the shutter member 5 a is engaged with the second abutmentsurface section 52 of the shutter member 5 b, while the first abutmentsurface section 51 of the other shutter member 5 b is engaged with thesecond abutment surface section 52 of the shutter member 5 a, as shownin FIGS. 14 and 15.

The shutter members 5 a, 5 b are each formed with an elongated opening54, engaged by one of a pair of guide pins 53, protuberantly formed onthe inner surface of the lower shell 7, as shown in FIG. 7. Theseelongated openings 54 are formed to a preset length from a mid portionof the chord towards the engagement openings 50 a, 50 b so that theshutter members 5 a, 5 b will be rotated between the closure positionand the opened position. The end of the elongated opening 54 towards theouter rim is provided with an engagement portion 55 engaged by the guidepin 53 of the lower shell 7 and with an elastic piece 56 af; thrustingthe guide pin 53 engaged with the engagement portion 55.

The disc cartridge 1 is provided with a second dust intrusionprohibiting section 57A for preventing the dust and dirt from beingintruded through a space between the aperture 24 of the main cartridgebody unit 2 and the paired shutter members 5 a, 5 b. The second dustintrusion prohibiting section 57A is provided between the lower shell 7and the shutter members 5 a, 5 b, as shown in FIG. 16. The second dustintrusion prohibiting section 57A is made up by a rib-like projection 57provided on the lower shell 7 for surrounding the aperture 24, as shownin FIG. 7, and by a groove-like recess 58 engaged by the rib-likeprojection 57 provided on the shutter members 5 a, 5 b, as shown in FIG.13. The rib-like projection 57, forming the second dust intrusionprohibiting section 57A, is protuberantly formed in the form of asubstantially planar H-shape so that the aperture 24 will be encircledby the inner surface of the inner shell 4. The portions of the rib-likeprojection 57, connecting to the outer peripheral wall 21 of the frontside and the back side, are formed as raised portions 57 a, 57 b, 57 cand 57 d of an increased height. Meanwhile, the rib-like projection 57is of a height of the order of 0.5 mm, with the height of the fourraised portions 57 a to 57 d being approximately several times as largeas the rib-like projection 57.

On the other hand, the groove-like recess 58 is formed in the majorsurface of the lower shell 7 of each of the shutter members 5 a, 5 b toa size and depth corresponding to those of the rib-like projection 57.This groove-like recess 58 is engaged by the rib-like projection 57,when the shutter members 5 a, 5 b are in the closure position, as shownin FIG. 16. The width-wise ends of the rib-like projection 57 and thegroove-like recess 58 are formed as inclined surfaces 58 a, 58 b, asshown in FIG. 16, so that, when the shutter members 5 a, 5 b are movedfrom the first position of closing the aperture 24 to the secondposition of opening the aperture 24, the rib-like projection 57 can beeasily disengaged from the groove-like recess 58.

Meanwhile, with the second dust intrusion prohibiting section 57A, whenthe rib-like projection 57 is engaged with the groove-like recess 58,the abutment surface between the groove-like recess 58 and the rib-likeprojection 57 is cranked in shape for assuring positive closure of thespace between the lower shell 7 and the shutter members 5 a, 5 b forpositively preventing dust and dirt from intruding into the inside ofthe main cartridge body unit 2.

The inner shell 4 is formed with protuberant substantiallytrapezoidally-shaped disengaging protrusions 59, in the vicinity of thepaired supporting shafts 49 a, 49 b, as shown in FIGS. 5, 10 and 11.These disengaging protrusions 59 are of approximately the same height asthe rib-like projection 57 and operate for disengaging the rib-likeprojection 57 from the groove-like recess 58 when the shutter members 5a, 5 b are moved from the closure position to the opened position.

It is noted that the width-wise ends of the rib-like projection 57 andthe groove-like recess 58, engaged with each other, are formed asinclined surfaces, as shown in FIG. 15, to assure facilitateddisengagement of the rib-like projection 57 from the groove-like recess58 when the shutter members 5 a, 5 b are moved from the closure positionto the opened position.

The shutter members 5 a, 5 b are each formed with a protuberant firstclosure piece 60 a, abutted by the raised portions 57 a, 57 c of therib-like projection 57, while being each formed with a protuberantsecond closure piece 60 b, abutted by the raised portions 57 b, 57 dthereof, as shown in FIGS. 12 and 13. The shutter members 5 a, 5 b arealso each formed with a cut-out 61 at the distal end of the secondabutment surface section 52 for allowing for entrance of the raisedportions 57 b, 57 d of the rib-like projection 57. The major surface ofeach of the shutter members 5 a, 5 b towards the lower shell 7 is formedwith an indented labyrinthine pattern 62, as shown in FIGS. 14 to 16.This indented labyrinthine patterns 62, comprised of plural parallelalternate recesses and lands, is formed inwards on the shutter members 5a, 5 b to form a third dust intrusion prohibiting section 62A. That is,when the shutter members 5 a, 5 b are superposed on the lower shell 7,the indented labyrinthine pattern 62 forms a space between the lowershell 7 and the shutter members 5 a, 5 b into which intrusion of dustand dirt is allowed to prevent intrusion of dust and dirt into theinside of the main cartridge body unit 2. Meanwhile, the numerousrecesses and lands of the indented labyrinthine pattern 62 forming thethird dust intrusion prohibiting section 62A are provided so as to beelongated in a direction intersecting the flow direction of dust anddirt intruded via the recording and/or reproducing aperture portion 24 aformed in the main cartridge body unit 2. That is, the indentedlabyrinthine pattern 62 is provided for extending substantially parallelto the lateral edges of the recording and/or reproducing apertureportion 24 a.

The assembling sequence of the above-described disc cartridge 1,according to the present invention, is as follows:

In assembling the disc cartridge 1, the upper shell 6 is placed with itsinner surface directed upwards, as shown in FIG. 5. The chuck plate 40is housed in the plate housing recess 41 of the upper shell 6, as thedisc thrusting portion 40 a is directed upwards. The disc thrustingportion 40 a is fitted from the fitting opening 42 a and, in this state,the plate retainer 42 is mounted in the plate housing recess 41 as withan adhesive. This causes the disc thrusting portion 40 a of the chuckplate 40 to be protruded from the fitting opening 42 a of the plateretainer 42, while causing the chuck plate 40 to be rotatablyaccommodated in the inner space defined by the plate housing recess 41and the plate retainer 42.

The optical disc 3 is housed within the inner peripheral wall 11 formingthe disc housing section of the upper shell 6.

The ring 43 of the inner shell 4 is engaged in the guide groove 13 ofthe upper shell 6 to overlie the optical disc 3. This rotatablyaccommodates the optical disc 3 in the disc housing section definedintermediate the upper shell 6 and the inner shell 4. It is noted thatregistration of the inner shell 4 relative to the upper shell 6 is to beachieved at the outset so that the aperture 44 of the inner shell 4 isin coincidence with the first and second pickup intrusion recesses 9, 12of the upper shell 6.

The paired shutter members 5 a and 5 b are then mounted to the innershell 4. Specifically, the engagement openings 50 a, 50 b are engaged bythe supporting shafts 49 a, 49 b of the inner shell 4, as the abutmentsurfaces of the shutter members 5 a and 5 b face each other. This allowsthe paired shutter members 5 a and 5 b to be mounted for rotation aboutthe supporting shafts 49 a, 49 b of the inner shell 4 as the center ofrotation. It is noted that registration of the paired shutter members 5a and 5 b with respect to the inner shell 4 is to be achieved at theoutset so that the abutment surfaces of the paired shutter members 5 aand 5 b will lie along the side edge of the aperture 44 of the innershell 4. Simultaneously as, before or after this position registration,the lock member 29 is mounted on the supporting shaft 25 of the lockhousing section, while the tab member 30 is housed within the tabhousing section.

The lower shell 7 then is superposed on the upper shell 6. As theperipheral wall sections 8, 21 of the upper and lower shells 6, 7 areabutted against each other, the positioning peripheral wall 22 of thelower shell 7 is engaged in the positioning recess 10 of the upper shell6. The positioning pin 20 of the upper shell 6 is fitted to thepositioning cap 28 of the lower shell 7. The dust-proofing peripheralwall 23, lower corner peripheral wall 26 and the lower tab peripheralwall 27 of the lower shell 7 are engaged in the first groove 16, secondgroove 17 and in the third groove 19 of the upper shell 6, respectively.

The guide pin 53 of the lower shell 7 is engaged in the elongatedopening 54 in the shutter members 5 a, 5 b. It is noted thatregistration between the lower shell 7 and the paired shutter members 5a, 5 b may be facilitated by previous position registration of thepaired shutter members 5 a, 5 b with respect to the inner shell 6. A setscrew, not shown, is threaded in the tapped hole of the positioning pin20 through the through-hole of the positioning cap 28. This secures thelower shell 7 to the upper shell 6 to form the main cartridge body unit2. At this time, the inner shell 4 and the paired shutter members 5 a, 5b are in the open positions, such that a portion of the optical disc 3is exposed to outside via the aperture 24 of the main cartridge bodyunit 2.

The gear 45 is acted on in this state to rotate the inner shell 4 in theopposite direction to cause the paired shutter members 5 a, 5 b to closethe aperture 24 of the main cartridge body unit 2. The above completesthe assembling operation of the disc cartridge 1. Thus, the disccartridge 1 according to the present invention can be assembledextremely easily with a smaller number of components.

As means for securing the lower shell 7 to the upper shell 6, adhesivesmay be used for securing the upper and lower shells 6, 7 together,instead of using fastening means, such as st screws.

With the above-described disc cartridge 1, information signals can berecorded and/or reproduced for the optical disc 3 using a disc drivingdevice 70 such as is shown in FIG. 17.

The disc driving device 70 includes an outer casing 71, formed by ahollow casing, and a main body unit, not shown, accommodated within theouter casing 71. This outer casing 71 includes a main casing unit 72opened in the upper and front surfaces, a casing lid 73 removablymounted on an upper part of the main casing unit 72 for closing itsupper side, and a front panel 74 removably mounted to a front side ofthe outer casing for closing the front side of the main casing unit 72and the casing lid 73.

At four places of the main casing unit, there are provided legs 72 aprotruded downwards. It is by these legs 72 a that the disc drivingdevice 70 is supported. The front panel 74 is a horizontally elongatedflat plate member, an upper portion of which includes a horizontallyelongated cartridge inserting/ejecting opening 75. This cartridgeinserting/ejecting opening 75 is of approximately the same size as thefront surface of the disc cartridge 1. This cartridge inserting/ejectingopening 75 is kept closed by an opening/closure door 76 provided on aninner side.

In introducing the disc cartridge 1 into the disc driving device 70, theopening/closure door is pressed by the front surface side of the disccartridge 1, until the disc cartridge 1 is inserted to a predeterminedposition, at which time the disc cartridge 1 is automatically gripped bya loading mechanism, not shown. The disc cartridge 1 is set on thechassis 1, with plural positioning recesses 38 being engaged by pluralpositioning pins, not shown, protuberantly formed on the chassis 1within the disc driving device 70.

Simultaneously as, before or after this setting of the disc cartridge,the inner shell 4 is rotated in one direction, by a shutteropening/closing mechanism, provided within the disc driving device 70,so that the paired shutter members 5 a, 5 b open the aperture 24 of themain cartridge body unit 2.

Specifically, when the disc cartridge 1 is inserted as far as apredetermined position from the cartridge inserting/ejecting opening 75,a rack rod 77 of the shutter opening/closure mechanism thrusts theoperating lug 32 a of the lock member 29 protruded from the lock opening35 a, as shown in FIG. 18. This unlocks the lock member 29 with respectto the inner shell 4. The rack rod 77 is further introduced into theopening for a rotor 35 b to cause a gear 77 a provided on the rack rod77 to mesh with the gear 45 of the inner shell 4.

Since the aperture 44 of the inner shell 4 is inclined to the maximumextent with respect to the aperture 24 of the main cartridge body unit2, the overlapped portions of the apertures 24, 44 are exposed, however,the overlapped aperture portions are closed by the paired shuttermembers 5 a, 5 b.

If then the rack rod 77 is intruded, as a result of the operation ofintroducing the disc cartridge, as shown in FIG. 19, the inner shell 4is rotated in one direction, as a result of meshing of the gear 77 a ofthe rack rod 77 with the gear 45 of the inner shell 4.

In an initial state in which the inner shell 4 commences its rotation,the lift-up lugs 48 of the inner shell 4 ride over the lift-up lugs 14of the guide groove 13, so that the shutter member 5 is clamped betweenthe inner shell 4 and the lower shell 7. Thus, a larger force isrequired in causing rotation of the inner shell 4. Referring to FIG. 20,the inner shell 4 is rotated in one direction, against the force offriction produced by the riding of the lift-up lugs 14, 48 relative toeach other. This disengages the lift-up lugs 14, 48 from each other toreduce the force of friction to permit the inner shell 4 to be rotatedsmoothly with only a small force.

By the inner shell 4 being rotated in one direction, the disengagingprotrusions 59 ride on the raised portions 57 a, 57 c of the rib-likeprojection 57 to set up a state in which the inner shell 4 is raisedrelative to the lower shell 7. This raises the shutter members 5 a, 5 btowards the upper shell 6 to disengage the rib-like projection 57 fromthe groove-like recess 58.

Since the engagement openings 50 a, 50 b of the paired shutter members 5a, 5 b are engaged with the supporting shafts 49 a, 49 b, the shuttermembers 5 a, 5 b are also rotated in one direction, as is the innershell 4. On the other hand, since the guide pin 53 of the lower shell 7is slidably engaged in the elongated openings 54 of the shutter members5 a, 5 b, the guide pin 53 is relatively moved in the elongated opening54 towards its inner peripheral end in keeping with rotation of theinner shell 4.

Thus, the paired shutter members 5 a, 5 b are moved from the slightlyopened state of FIG. 21, through the states shown in FIGS. 22, 23 and 24to a position gradually opening the aperture 44 of the inner shell 4.When the inner shell 4 is rotated to a condition in which the aperture44 of the inner shell 4 is approximately coincident with the aperture 24of the main cartridge body unit 2, as shown in FIG. 25, the aperture 24of the main cartridge body unit 2 is completely opened.

The disc driving device 70 is now in such a state in which the turntable78 for rotationally driving the optical disc 3 and the optical head 79for recording and/or reproducing information signals on or from theoptical disc 3 may be inserted into the inside of the disc cartridge 1,as shown in FIG. 9.

That is, in the present disc driving device 70, when the turntable 78 ismoved towards the disc cartridge 1 or when the disc cartridge is movedtowards the turntable 78, a chuck magnet 78 a of the turntable 78 issucked towards the chuck plate 40, through the center opening 3 a of theoptical disc 3, so that the center portion of the optical disc 3 isclamped between the turntable 78 and the chuck plate 40. The opticaldisc 3 is now chucked in position on the turntable 78 and hence is runin rotation under the driving force of a spindle motor 80. The opticaldisc 3 is also chucked on the turntable 78 for setting the height-wiseposition thereof in the inside of the main cartridge body unit 2.

On the other hand, the optical head 79 is moved along the radius of theoptical disc 3 so that at least a portion of the optical head 79 isintruded from outside the outer rim of the disc cartridge 1 through theapertures 24, 44 into the inside of the disc cartridge 1. Moreover, theoptical head 79 faces a signal readout surface R, as the lower surfaceof the optical disc 3, with a preset separation within the disccartridge 1.

It is noted that, with the disc cartridge 1, a connecting portion 43 aoperating for bridging the aperture 44 of the inner shell 4 is set to aheight such that the connecting portion 43 a is not protruded towardsthe lower shell 7 with respect to the signal readout surface R of theoptical disc 3, as shown in FIGS. 26 and 27.

More specifically, the connecting portion 43 a of the inner shell 4 isset so as to be flush with or lower in height than an outer peripheralwall 8 a of the upper shell 6, exposed to outside via the aperture 24 ofthe main cartridge body unit 2. An inner peripheral wall 11 a of theupper shell 6, exposed to outside via the aperture 24 of the maincartridge body unit 2, is set so as to be flush with or lower in heightthan the connecting portion 43 a of the inner shell 4.

With the height h₁ of the outer peripheral wall 8 a of the upper shell6, exposed to outside through the aperture 24 of the main cartridge bodyunit 2, the height h₂ of the connecting portion 43 a of the inner shell4 and with the height h₃ of the inner peripheral wall 11 a of the uppershell 6, exposed to outside through the aperture 24 of the maincartridge body unit 2, the relationship of h₁>h₂>h₃ is met.

In this case, if a minor offset caused by rotation is produced betweenthe ring 43 of the inner shell 4 and the guide groove 13 of the uppershell 6, the optical head 79 may be optimally intruded into the insideof the disc cartridge 1 without the optical head 79 interfering with theconnecting portion 43 a of the inner shell 4. That is, with the presentdisc cartridge, the optical head 79, moved substantially horizontally,may be optimally intruded into the inside of the disc cartridge 1 fromoutside the outer rim of the disc cartridge 1 through the apertures 24,44.

Consequently, with the disc cartridge 1, the position relationshipbetween the optical disc 3 and the optical head 79 may be maintainedoptimally to assure high operational reliability in a manner free frompossible damages to the optical head 79.

When the disc cartridge 1 according to the present invention is loadedin the cartridge loading position in the disc driving device 70, theoptical disc 3, housed within the main cartridge body unit 2, is loadedon the turntable 78. By the chuck plate 40 being sucked by a magnet, notshown, provided on the turntable 78, so as to be clamped between theturntable 78 and the chuck plate 40, the optical disc 3 may be rotatedin unison with the turntable 78. When the spindle motor is run inrotation, the optical disc is run in rotation, as one with the turntable78, at a constant linear velocity. At this time, the shutter members 5a, 5 b are moved, such that the optical head 79 faces the optical disc 3via the recording and/or reproducing aperture 24 now opened. By theoptical head 79 being moved along the radius of the rotationally drivenoptical disc 3 and by the signal recording area of the optical disc 3being scanned by the light beam radiated from the optical head 79, theinformation signals recorded on the optical disc 3 may be read out, orthe information signals may be written on the optical disc 3.

In discharging the disc cartridge 1 from the disc driving device 70, aneject button, not shown, provided on e.g. the front panel 74, is actedon, whereby the loading mechanism performs the ejecting operation tomove the disc cartridge 1 towards the cartridge inserting/ejectingopening 75 to cause relative receding movement of the rack rod 77. Bythe rack rod 77 performing a receding movement, the operation which isthe reverse of that in inserting the disc as described above occurs,that is, the inner shell 4 is rotated in the opposite direction, withthe paired shutter members 5 a, 5 b closing the aperture 24 of the innershell 4.

Specifically, the shutter members 5 a, 5 b are gradually moved in thereverse direction from the completely opened state shown in FIG. 25,through the states shown in FIGS. 23, 22 and 21, in this order, up to aposition of completely closing the aperture 44 of the inner shell 4. Atthis time, the lift-up lugs 48 of the inner shell 4 is not engaged withthe lift-up lugs 14 of the lower shell 7, such that the inner shell 4may be rotated smoothly with only a small force.

When the inner shell 4 is rotated to a state in which the aperture 44 ofthe inner shell 4 is tilted to the maximum extent with respect to theaperture 24 of the inner shell 4, the aperture 24 of the main cartridgebody unit 2 is closed completely.

Since the lift-up lugs 48 of the inner shell 4 ride on the lift-up lugs14 of the lower shell 7, a relatively large force is required forsubsequent rotation of the inner shell 4, because of the resistanceoffered by the force of friction.

With rotation of the inner shell 4, the guide pin 53 performs relativemovement in the inside of the elongated opening 54 towards the outerperipheral end. The elastic force is produced in the elastic piece 56 bythe guide pin 53 contacting and thrusting the elastic piece 56. By thiselastic force, the abutment surfaces of the paired shutter members 5 a,5 b compress against each other, thus improving the hermetic sealing.

Moreover, with the present disc cartridge 1, the first abutment surfacesection 51 of the shutter member 5 a is engaged with the second abutmentsurface section 52 of the other shutter member 5 b, while the firstabutment surface section 51 of the shutter member 5 b is engaged withthe second abutment surface section 52 of the other shutter member 5 a.

In this case, since the abutment surfaces of the shutter members 5 a, 5b are optimally superposed together, the so-called labyrinth effect isproduced, thus preventing dust and dirt from being intruded via a spacebetween the paired shutter members 5 a, 5 b. That is, the dust intrusionprohibiting section is formed. In this case, since the abutment surfacesof the shutter members 5 a, 5 b are optimally superposed together, it ispossible to prevent the paired shutter members 5 a, 5 b from beingdeformed.

The rack rod 77 then is receded further to disengage the gear 77 a ofthe rack rod 77 from the gear 45 of the inner shell 4. The operatingprojection 32 a of the lock member 29 then is projected from the lockopening 35 a so that the stopper boss 33 a of the stopper piece 33 isengaged with the gear 45 of the inner shell 4. This halts rotation ofthe inner shell 4 in the disc cartridge 1 to set up a so-called lockcondition so that the state of closure of the apertures 24, 44 by theshutter members 5 a, 5 b may be reliably maintained and hence theinadvertent opening operation of the shutter members 5 a, 5 b by theuser may be prevented positively.

Moreover, in the present disc cartridge, since the lift-up lugs 48 ofthe inner shell 4 ride on the lift-up lugs 14 of the lower shell 7, theapertures 24, 44 may be maintained in the fully closed state under theown weight of the shutter members 5 a, 5 b and the force of frictionproduced between the inner shell 4 and the lower shell 7.

With the present disc driving device 70, the opening/closure door 76opens the cartridge inserting/ejecting opening 75 to permit the disccartridge 1 to be automatically ejected by the loading mechanism via theopened cartridge inserting/ejecting opening 75.

Meanwhile, the inner shell 4, forming the disc cartridge 1 according tothe present invention, is formed using a resin molded product 100,formed as shown in FIGS. 28 and 29. The resin molded product 100includes a first molded portion 100A and a second resin molded portion100C formed centrally of and as one with the first molded portion 100Athrough a flanged thin-walled portion 100B, as shown in FIGS. 28 and 29.The second resin molded portion 100C includes a trace 100D of a resininjecting port or gate used at the time of molding.

After the flanged thin-walled portion 100B is cut off and the secondresin molded portion 100C is removed, the first molded portion 100A isassembled into the disc cartridge 1 to form the inner shell 4, as shownin FIGS. 30 and 31.

The second resin molded portion 100C, provided with a resin injectionport of the resin molded product 100, is provided, along with theflanged thin-walled portion 100B, at a position of the second resinmolded portion in register with the aperture 44 of the inner shell 4.That is, by severing the second resin molded portion 100C along with theflanged thin-walled portion 100B from the resin molded product 100, thefirst molded portion 100A forms the inner shell 4 provided with theaperture 44.

The resin molded product 100, which is to form the inner shell 4, ismanufactured by using an injection molding device 200, shown in FIG. 32.This injection molding device 200 includes a fixed metal die 201 and amovable metal die 202. Between the fixed metal die 201 and the movablemetal die 202, there is formed a cavity 203, as a mold cavity, forforming the resin molded product 100. The cavity 203 includes a firstcavity portion 203 a for forming the first molded portion 100A, a secondcavity portion 203 b for forming the flanged thin-walled portion 100Band a third cavity portion 203 c for forming the second resin moldedportion 100C.

The fixed metal die 201 includes a gate bush 204, as a resin injectionport, at a position thereof in register with the mid portion of thethird cavity portion 203 c. The second cavity portion 203 b is asemi-circular film gate. The movable metal die 202 is provided with agate cutting punch 205.

In the present injection molding device 200, when the molten resin isinjected into the cavity 203 through the gate bush 204, the molten resinis diffused radially, about the gate 204 as center, so as to be injectedinto the third cavity portion 203 c and into the first cavity portion203 a. By injecting the molten resin into the third cavity portion 203 cand into the first cavity portion 203 a, and by maintaining a presetpressure between the fixed metal die 201 and the movable metal die 202,the molten resin is charged even into niches of the third cavity portion203 c and into the first cavity portion 203 a, for forming the resinmolded product 100 comprised of the first to third molded portions.

When the resin molded product 100 has reached a temperature not higherthan a preset temperature, before the resin molded product 100 is cooledand solidified in the cavity 203, the flanged thin-walled portion 100Bis severed, using the gate cutting punch 205. The movable metal die 202then is moved in a direction away from the fixed metal die 201. Thefirst and second molded portions 100A and 100C, severed at the flangedthin-walled portion 100B, are taken out from the injection moldingdevice 200.

In case the resin molded product 100 is molded using the injectionmolding device not provided with the gate cutting punch 205, the resinmolded product 100 molded by the injection molding device is set on alower jig 211 of a gate cutting device 210 and is retained by an upperjig 212 to sever the flanged thin-walled portion 100B by a gate cuttingpunch 213, as shown in FIG. 33.

The inner shell 4, manufactured by the method of the present invention,is formed from the resin molded product 100, by removing the secondresin molded portion 100C, inclusive of a portion destined to be a resininjection port at the time of casting, and using only the first moldedportion 100A not having the trace of the gate 100D, so that the innershell may be manufactured to a high molding accuracy. Moreover, sincethere is no risk of producing micro-sized projections ascribable to thegate trace 100D on the outer peripheral surface, the inner shell 4 maybe mounted within the main cartridge body unit 2 as smooth rotationthereof in the main cartridge body unit 2 is guaranteed.

In the manufacture of the inner shell 4 according to the presentinvention, the first molded portion 100A, forming the inner shell 4, maybe separated from the second molded portion by severing the flangedthin-walled portion 100B interconnecting the first molded portion 100Aand the second resin molded portion 100C, so that manufacture may befacilitated. Moreover, since the cutting of the flanged thin-walledportion 100B is achieved in the metal die by a punch provided to themetal die of the injection molding device used for casting the resinmolded product 100 forming the inner shell 4, the manufacture is againfacilitated.

Although the foregoing description is made for a case of a disccartridge employing an optical disc as an information recording medium,the present invention may also be applied to a magnetic disc, such as amagneto-optical disc or a floppy disc, and to a variety of otherdisc-shaped recording mediums. Although the foregoing description ismade for a case in which the information recording and/or reproducingapparatus is a disc recording and/or reproducing apparatus, the presentinvention may, of course, be applied to a disc recording apparatus or adisc reproducing apparatus, that is an apparatus enabling only one ofthe recording and the reproducing operations.

Although the foregoing description is made for a case in which theaperture 24 is provided in the lower shell 7 of the main cartridge bodyunit 2, it is also possible to provide an aperture similar to thatformed in the upper shell 6 to permit the optical disc to be accessedsimultaneously from both the upper and lower shells 6, 7. It is alsopossible to vary the shape of the apertures 24 to enable plural discssimultaneously.

INDUSTRIAL APPLICABILITY

With the disc cartridge of the present invention, provided with a dustintrusion prohibiting section for prohibiting intrusion of dust into themain cartridge body unit, a superior dust-proofing effect may bedisplayed such that even micro-sized dust may be prevented from beingintruded into the main cartridge body unit accommodating the disc-shapedrecording medium.

Moreover, since the disc cartridge of the present invention is able toprevent intrusion of dust and dirt into the main cartridge body unit,while the interconnecting portion of the inner shell is of such a heightthat it is not protruded towards the lower shell with respect to thelower surface of the disc-shaped recording medium, so that the recordingand/or reproducing head may be satisfactorily introduced into the insideof the main cartridge body unit, without interfering with the connectingportion of the inner shell, as the recording and/or reproducing head isapproached towards the disc-shaped recording medium, thus achieving thereduced size of the disc cartridge.

In addition, since the inner shell housed in the main cartridge bodyunit of the disc cartridge according to the present invention can bemolded to a high accuracy, a superior dust-proofing effect may bedisplayed, such that even micro-sized dust may be prevented from beingintruded into the main cartridge body unit, while the recording and/orreproducing aperture provided in the main cartridge body unit can beopened or closed smoothly.

1. A disc cartridge comprising: a disc-shaped recording medium; a maincartridge body unit including an upper shell and a lower shell, saidmain cartridge body unit accommodating said disc-shaped recording mediumfor rotation therein, wherein a peripheral wall section of said uppershell and a peripheral wall section of said lower shell abut againsteach other, and at least a portion of the peripheral wall section ofsaid lower shell being opened to form an open end, with an aperturebeing formed in said main cartridge body unit beginning from said openend for exposing a portion of said disc-shaped recording medium tooutside across the inner and outer rims of the disc-shaped recordingmedium; an inner shell engaged in a guide groove formed between an outerperipheral wall section and an inner peripheral wall section of saidupper shell so as to be supported for rotation therein, said inner shellincluding a connecting portion engaged in said guide groove, said innershell also including an aperture in register with said aperture in saidmain cartridge body unit; and a shutter member movable by rotation ofsaid inner shell between a position closing said aperture in said maincartridge body unit and a position opening said aperture in said maincartridge body unit, wherein said inner shell includes a first moldedportion, provided with a recording and/or reproducing aperture, a secondmolded portion having a resin injection port and molded at a positionwhere said aperture is formed, and a flanged thin-walled sectionconnecting said first and second molded portions to each other.
 2. Thedisc cartridge as recited in claim 1 wherein said flanged thin-walledsection is formed to a semi-circular shape within said aperture in saidinner shell.